National Instruments SCXI-1190/1191 - Manual (Page 25)

Chapter 2 Using the SCXI-119X
© National Instruments Corporation 2-3 SCXI-1190/1191 User Manual
Connections that exceed any of the maximum signal ratings on the SCXI-119X can create
a shock or fire hazard or can damage any or all of the devices connected to the SCXI-119X.
National Instruments is not liable for any damages or injuries resulting from incorrect
signal connections.
Clean the instrument and accessories by brushing off light dust with a soft, nonmetallic
brush. Remove other contaminants with a stiff nonmetallic brush. The unit must be
completely dry and free from contaminants before returning to service.
RF Switching Precautions
The SCXI-119X is a reflective switch , meaning that any channels not
switched to the common channel are unterminated, and any signal on an
unterminated channel is reflected to its source. For most low-power
switching applications this reflection is not a problem. However, operation
with an unterminated output can damage some high-power RF sources.
Consult your RF source documentation for more information about
connecting to unterminated channels.
Warning Do not exceed the channel-to-ground rating of 24 V on the SCXI-1190 and
30 V
rms
or DC for the SCXI-1191. Any connections that exceed the maximum voltage for
the SCXI-119X can result in an electrical shock hazard and damage to the switch module
and any or all of the modules connected to the SCXI backplane. National Instruments is
not liable for any damages or injuries resulting from exceeding maximum voltage ratings.
Refer to Appendix A,
Specifications , for specific information.
Caution Always disconnect all signals from the front connectors and power down the
SCXI chassis before removing the SCXI-119X from the chassis. Observe electrostatic
discharge handling precautions during and after removal of the module, or when
connecting and disconnecting signals on the front panel.
Contact Protection
Caution The contacts of the relay are rated for a life of 5
×
10 6 mechanical operations
when operated with no signal or a very small signal present. At full rated power of 1 A at
24 VDC for the SCXI-1190 or of 30 VDC at 1/3 ADC for the SCXI-1191, the life of the
switch is downgraded to 100,000 operations. If your setup allows, it is always best to turn
off the input signals connected to the switch module during the switching operation to
avoid contact arcing within the switch. Switching large inductive loads can also cause
contact arcing. In such instances, install a flyback diode or varistor across the inductance
to protect the switch.